class_docstr: Base class for TurntableCamera and ArcballCamera
code: def distance(self, distance):
      if distance is None:
          self._distance = None
      else:
          self._distance = float(distance)
      self.view_changed()
  
imports: from __future__ import division
  import math
  import numpy
  from .base_camera import BaseCamera
  from ...util import keys, transforms
  from ...visuals.transforms import MatrixTransform
label_desc: Use image node_id 3 for calling the Base3DRotationCamera obj's underlying member method code with example usage: obj.distance(distance) without return types